The present invention relates in general to the field of microelectronic element mounting and connection, and more particularly, to connection components and semiconductor chip packages using anisotropic conductive adhesive material interconnection and to assembly methods therefor.
Microelectronic elements such as semiconductor chips are connected to external circuitry, such as the circuitry of a supporting substrate or circuit panel, through electrical contacts on the front face of the chip. Various processes for making these interconnections use prefabricated arrays of leads or discrete wires. For example, in tape automated bonding processes, a dielectric supporting tape such as a thin film of polyimide, includes an array of metallic leads on one surface of the dielectric film. The metallic leads are aligned with the contacts on the front face of the chip. The dielectric film is juxtaposed with the chip so that the leads extend over the front or contact bearing surface on the chip. The leads are then bonded to the contacts of the chip, as by ultrasonic or thermocompression bonding. The terminals on the dielectric film may then be connected to external circuitry for electrically interconnecting the chip and the external circuitry.
The evolution of the semiconductor art in recent years has created a continued demand for semiconductor chip packages having progressively greater numbers of contacts and leads in a given amount of space. An individual chip may require hundreds or even thousands of contacts, all within the area of the front face of the chip. Certain complex semiconductor chips currently being used have contacts spaced apart from one another at extremely small center-to-center distances. With such closely-spaced contacts the leads connected to the chip contacts must be extremely fine structures, typically having a smaller bonded surface than the contacts onto which they are bonded so that the adjacent leads do not electrically short.
In the bonding process of some assembly methods, the bonding region of each lead is engaged by a bonding tool which bears on the top surface of the lead in the bonding region and forces the lead downwardly into engagement with the contact. Energy supplied through the bonding tool causes the bonding metal to join with the contact. Typically, the leads are bonded to the chip contacts with the bonding tool using heat, force, ultrasonic energy, or a combination of two or more thereof, for a given time period. If incorrect force, heat and/or ultrasonic energy is used, the bond between the leads and the contacts may be too weak to withstand thermal cycling stresses during operation of the chip (heating and cooling cycles during operation). Also, the bonding tool may create areas of the lead which are prone to early fatigue during thermal cycling because of excessive non-uniform deformation in the bonding region, typically causing early breaks in the lead at the point the lead bends up from the chip surface.
In various microelectronic devices, it is also desirable to provide a connection between two components, which can accommodate relative movement between the components. For example, where a semiconductor chip is mounted to a circuit board, thermal expansion and contraction of the chip and circuit board can cause the contacts on the chip to move relative to the corresponding electrically conductive features of the circuit board. This can occur during service and can also occur during manufacturing operations as, for example, during soldering operations on the circuit board.
As illustrated in U.S. Pat. No. 5,518,964 (xe2x80x9cthe ""964 Patentxe2x80x9d), the disclosure of which is incorporated herein by reference, movable interconnections between elements such as a semiconductor chip and another element can be provided by first connecting leads between the elements and then moving the elements away from one another through a preselected displacement so as to bend the leads. For example, a connection component may incorporate a dielectric body and leads extending along a bottom surface of the dielectric body. The leads may have first or fixed ends permanently attached to the dielectric element and connected to electrically conductive features such as terminals, traces or the like on the dielectric body. The leads may also have second ends releasably attached to the dielectric body. The dielectric body, with the leads thereon, may be juxtaposed with the chip and the second ends of the leads may be bonded to contacts on the chip.
Following bonding, the dielectric body and chip are moved away from one another, thereby bending the leads towards a vertically extensive disposition. During or after movement, a curable material such as a liquid composition may be introduced between the elements. This may be cured to form a compliant dielectric layer such as an elastomer or gel surrounding the leads. The resulting packaged semiconductor chip has terminals on the dielectric body connection component which are electrically connected to the contacts on the chip but which can move relative to the chip to compensate for thermal effects. The packaged chip may be mounted to a circuit board by solder-bonding the terminals to conductive features on the circuit board. Relative movement between the circuit board and the chip due to thermal effects is taken up in the moveable interconnection provided by the leads and the compliant layer.
There is further disclosed in the ""964 Patent a connector for use in making connections between two other microelectronic elements which is fabricated by a generally similar thus far described process. For example, in one embodiment a dielectric body having terminals and leads as discussed above is connected to terminal structures on a temporary sheet. The temporary sheet and dielectric body are moved away from one another so as to bend the leads, and a liquid material is introduced around the leads and cured to form a compliant layer between the temporary sheet and the dielectric body. The temporary sheet is then removed, leaving the tip ends of the terminal structures projecting from a surface of the compliant layer. Such a component may be used, for example, by engaging it between two other components. For example, the terminal structures may be engaged with a semiconductor chip, whereas the terminals on the dielectric body may be engaged with a circuit panel or other microelectronic component. Variation of the above described structures are disclosed in U.S. Pat. No. 6,117,694 (xe2x80x9cthe ""694 Patentxe2x80x9d) the disclosure of which is incorporated herein by reference.
In copending U.S. patent application Ser. No. 09/237,072, filed Jan. 25, 1999 and entitled xe2x80x9cCompliant Semiconductor Package With Anisotropic Conductive Material Interconnects and Methods Thereforxe2x80x9d (xe2x80x9cthe ""072 Applicationxe2x80x9d), the disclosure of which is incorporated herein by reference, there is described a microelectronic package including a first microelectronic element having a front face including a plurality of contacts and a second microelectronic element including terminals accessible at a surface thereof and a plurality of flexible leads. Each of the flexible leads have a terminal end connected to one of the terminals and a tip end opposite the terminal end. Each flexible lead extends away from the second microelectronic element and is electrically interconnected with the plurality of contacts of the first microelectronic element. An anisotropic conductive material is interposed between each of the tip ends of the flexible leads and the contact associated therewith.
There is further described in the ""072 Application a method of making a microelectronic package which includes providing a first microelectronic element having a front face including a plurality of contacts. An anisotropic conductive material is provided over each one of the plurality of contacts. A second microelectronic element is provided having terminals accessible at a surface thereof and including a plurality of flexible leads. Each of the leads has a terminal end attached to one of the terminals and a tip end offset from the terminal end. The first and second microelectronic elements are juxtaposed with one another. The tip ends of the flexible leads and the contacts are electrically interconnected so that the flexible leads extend away from the second microelectronic element with the anisotropic conductive material interposed between the tip ends and the contacts.
Akagawa, U.S. Pat. No. 5,677,576 discloses a semiconductor package including a semiconductor chip having one surface provided with an insulating passivation film having openings exposing aluminum contact pads formed on the surface of the semiconductor chip in a predetermined pattern. An anisotropic conductive sheet is formed over the passivation film and the contact pads. The anisotropic conductive sheet is formed of a resin containing conductive fillers such as metallic powders whereby the application of pressure to the film results in electrical conductivity in the pressed direction due to the continuity of the conductive fillers caused by the pressure. The metallic powders may be, for example, metallic particles in the nature of resin particles coated with nickel plated layers or the like or metallic particles such as of gold, nickel or the like.
Electrical conductive circuit patterns are formed in a predetermined arrangement on the exposed surface of the anisotropic conductive sheet. The circuit patterns are formed by adhering a metallic foil, such as a copper foil to the anisotropic conductive sheet and etching the foil in conformity with the predetermined circuit patterns. A photoresist film is deposited over the anisotropic conductive sheet and the circuit patterns. The photoresist film is provided with openings in the nature of via holes for receiving conductive bumps to provide external termination to the circuit patterns. By compressing the anisotropic conductive sheet in the region overlying the contact pads, electrical continuity to the circuit patterns is provided.
Tang, et al., U.S. Pat. No. 5,749,997 discloses another semiconductor device using an anisotropic conductive sheet. The device includes a semiconductor chip supporting on its major surface a plurality of composite bumps. The bumps are formed of a polymer body such as polyamic acid polyimide covered by a conductive metal coating such as a composite of chrome/gold or nickel/gold. An anisotropic conductive sheet is compressed over the composite bumps and the surface of the semiconductor chip. A dielectric layer having leads formed thereon such as in the conventional tape automated bonding process is arranged overlying the surface of the anisotropic conductive sheet. The leads may be fully supported by the dielectric sheet, or have portions extending within a window formed within the sheet. In either event, the dielectric sheet is arranged with the leads having one end overlying each of the composite bumps. Upon compression of the anisotropic conductive sheet, the conductive particles therein will make electrical contact with the leads and the conductive metal coating on the composite bumps.
Chillara, U.S. Pat. No. 5,627,405 discloses an anisotropic conductive sheet adhered to the surface of an integrated circuit semiconductor chip which includes a plurality of input/output terminals. The anisotropic conductive sheet is used to electrically couple the semiconductor chip directly to terminals on a printed circuit board, to leads of a lead frame, to traces on various substrate structures and the like.
Notwithstanding the foregoing known use of an anisotropic conductive sheet, there is still the need for improvements in microelectronic packages and methods of manufacturing same. In particular, there is the need for improvements in microelectronic packages which eliminate metal-to-metal bonding which is known to require the use of high temperature/pressures during thermocompression or thermosonic bonding. There is further the need for providing improved methods for making such microelectronic packages which will minimize deformation of the flexible leads thereby minimizing the potential for fatigue problems. Still further, there is the need for such microelectronic packages and methods for manufacturing same which provide for the use of narrow flexible leads which enables the obtaining of very fine pitches so as to accommodate more leads in a given space.
In accordance with one embodiment of the present invention there is described a connection component for a microelectronic element, the component comprising a body of dielectric material having opposing first and second surfaces, a plurality of elongated leads extending through the body between the first and second surfaces, the leads having a first end accessible at the first surface and a second end accessible at the second surface, and a layer of anisotropic conductive material overlying the first ends and the first surface of the body for electrical connection of the leads to a microelectronic element.
The aforesaid connection component wherein the dielectric material is flexible or rigid, wherein the first and second ends of the leads are offset from each other, and further including a plurality of contacts on the first surface in electrical contact with the first ends of the leads, wherein the plurality of contacts are formed from a portion of the first ends of the leads.
The anisotropic conductive material can be provided in the form of a paste or a preformed sheet, provided on the first surface of the body as an adhesive material.
The aforesaid connection component further including a layer of dielectric material on the second surface of the body, further including a plurality of conductors extending through the layer of dielectric material in electrical contact with the second ends of the leads, wherein the plurality of conductors comprise lined vias.
The aforesaid connection component wherein the layer of anisotropic conductive material is provided on the first surface of the body and the first ends of the leads, wherein the layer of anisotropic conductive material is provided on the second surf ace of the body and the second ends of the leads, and wherein the first ends are horizontally displaced from the second ends.
In accordance with another embodiment of the present invention there is described a connection component for a microelectronic element having a plurality of contact terminals arranged in an array, the component comprising a body of polymer material having opposing planar first and second surfaces, a plurality of elongated leads extending through the body between the first and second surfaces, the leads having a first end accessible at the first surface and a second end accessible at the second surface, a plurality of contacts on the first surface in electrical contact with the first ends of the leads, the plurality of contacts arranged in an array corresponding to the array of the plurality of contact terminal pads on the microelectronic element, and a layer of anisotropic conductive material overlying the first surface of the body and the plurality of contacts.
The aforesaid connection component further includes a layer of dielectric material on the second surface of the body and includes a plurality of conductors extending through the layer of dielectric material in electrical contact with the second ends of the leads, wherein the layer of anisotropic conductive material is provided on the first surface of the body and the layer of the anisotropic conductive material is further provided on the second surface of the body.
In accordance with another embodiment of the present invention there is described a microelectronic package comprising, a first microelectronic element having a front face including a plurality of contact terminals, a connector comprising a body of dielectric material having opposing first and second surfaces, the first surface facing the front face of the microelectronic element, a plurality of elongated leads extending through the body between the first and second surfaces, the leads having a first end accessible at the first surface and a second end accessible at the second surface, the first ends of the leads facing in alignment with the plurality of contact terminals on the first microelectronic element, and a layer of anisotropic conductive material between the front face of the microelectronic element and the first surface of the body, the anisotropic conductive material providing electrical continuity between the plurality of contact terminals and the leads.
The aforesaid microelectronic package further includes a plurality of contacts on the first surface in electrical contact with the first ends of the leads, wherein the dielectric material is flexible or rigid and the anisotropic conductive material is an adhesive material.
The aforesaid microelectronic package wherein the first and second ends of the leads are offset from each other and further including a plurality of contacts formed from a portion of the first ends of the leads, wherein the anisotropic conductive material is provided in the form of a paste or a preformed sheet.
The aforesaid microelectronic package wherein the layer of the anisotropic conductive material is provided on the first surface of the body and the first ends of the leads, and wherein the layer of the anisotropic conductive material is provided on the second surface of the body and the second ends of the leads and further including a layer of dielectric material on the first surface of the body, wherein the plurality of vias extend through the layer of dielectric material in electrical contact with the second ends of the leads.
The aforesaid microelectronic wherein the layer of anisotropic conductive material is provided on the front face of the first microelectronic element, wherein the first microelectronic element comprises a semiconductor chip, further including a second microelectronic element disposed on the second surface of the body, and wherein the second microelectronic element includes a plurality of second contact terminals connected to the second ends of the leads.
The aforesaid microelectronic package further comprising a second layer of anisotropic conductive material between the second microelectronic element and the second surface of the body, the second layer of anisotropic conductive material providing electrical continuity between the second contact terminals and the second ends, wherein the plurality of contact terminals are arranged in an array and the first ends of the leads are arranged in a corresponding array.
In accordance with another embodiment of the present invention there is described a method of making a connection component for a microelectronic element, the method comprising providing a body of dielectric material having opposing first and second surfaces and a plurality of elongated leads extending therethrough between the first and second surfaces, the leads having a first end accessible at the first surface and a second end accessible at the second surface, and providing a layer of anisotropic conductive material overlying the first ends and the first surface of the body for electrical connection to a microelectronic element.
The aforesaid method wherein the dielectric material is flexible or rigid and further includes forming the plurality of leads whereby the first and second ends are offset from each other.
The aforesaid method further including providing the layer of the anisotropic conductive material on the first surface of the body, further including providing the layer of the anisotropic conductive material on the second surface of the body, further including forming a plurality of contacts on the first surface in electrical contact with the first ends of the leads, further including providing a layer of dielectric material on the second surface of the body, further including providing a plurality of conductors extending through the layer of dielectric material in electrical contact with the second ends of the leads, and wherein the plurality of conductors comprise lined vias.
In accordance with another embodiment of the present invention there is described a method of making a microelectronic package, the method comprising providing a first microelectronic element having a front face including a plurality of first contact terminals, forming a body of dielectric material having opposing first and second surfaces and a plurality of elongated leads extending therethrough between the first and second surfaces, the leads having a first end accessible at the first surface and a second end accessible at the second surface, arranging the first surface of the body opposing the front face of the first microelectronic element, providing a layer of anisotropic conductive material between the front face of the microelectronic element and the first surface of the body, and adhering the first microelectronic element to the body whereby the anisotropic conductive material provides electrical continuity between the plurality of contact terminals and the leads.
The aforesaid method further including forming a plurality of contacts on the first surface in electrical contact with the first ends of the leads, the plurality of contacts arranged in alignment with the plurality of contact terminals, further including forming the plurality of leads whereby the first and second ends are offset from each other, wherein the layer of anisotropic conductive material is applied to the first surface of the body, wherein the layer of anisotropic conductive material is applied to the front face of the first microelectronic element.
The aforesaid method wherein the anisotropic conductive material is further applied to the second surface of the body, further including providing a layer of dielectric material on the second surface of the body, further including providing a plurality of conductors extending through the layer of dielectric material in electrical contact with the second ends of the leads.
The aforesaid method further including a second microelectronic element disposed on the second surface of the body, wherein the second microelectronic element includes a plurality of second contact terminals connected to the second ends of the leads, further including a layer of anisotropic conductive material on the second surface for electrically connecting the second ends of the leads to the plurality of second contact terminals, and further including a plurality of contacts integrally formed as a portion of the first ends of the leads adjacent the first surface. In accordance with another embodiment of the present invention there is described a connector for a microelectronic element, the connector comprising a body of dielectric material having opposing first and second surfaces, a plurality of elongated leads extending through the body between the first and second surfaces, the leads having a first end at the first surface and a second end at the second surface, and a layer of anisotropic conductive material overlying the first surface and the first ends of such leads.
The aforesaid connector wherein the anisotropic conductive material is applied on the first surface and wherein the anisotropic conductive material is provided in the form of a preformed sheet.
In accordance with another embodiment of the present invention there is described a microelectronic package comprising, a first microelectronic element having a front face including a plurality of first contact terminals, a printed circuit board having a front face including a plurality of second contact terminals, a connector comprising a body of dielectric material having opposing first and second surfaces, the first surface facing the front face of the microelectronic element, a plurality of elongated leads extending through the body between the first and second surfaces, the leads having a first end accessible at the first surface and a second end accessible at the second surface, the first ends of the leads facing in alignment with the plurality of contact terminals on the first microelectronic element, and a first layer of anisotropic conductive material between the front face of the microelectronic element and the first surface of the body, the anisotropic conductive material providing electrical continuity between the plurality of contact terminals and the leads, and the plurality of second contact terminals electrically connected to the second ends of the leads.
The aforesaid microelectronic package further includes a second layer of anisotropic conductive material provided between the front face of the printed circuit board and the second surface of the body, the anisotropic conductive material providing electrical continuity between the plurality of second contact terminals and the leads.